function checkPhone(phonenumber){
    return /^1[356789]\d{9}$/.test(phonenumber);
}
function checkEmail(email) {
    return /^[A-Za-z\d]+([-_.][A-Za-z\d]+)*@([A-Za-z\d]+[-.])+[A-Za-z\d]{2,4}$/.test(email)
}